The Seven Particular Parts: Ditch Profiles and the Mid-Ditch Wall
Depths and widths of ditch and bank, with a pointed mid-ditch wall and bevels marked a and b
A text page (folio 95v) turning from the common parts of fortresses to the seven 'particular' parts and then treating the first of them, the ditch, in detail. Leonardo lists the seven topics (ditches, ravelins, outer turrets, ditch-defences, walls, drawbridges and corridors, principal towers) and gives dimensions: ditches 40 to 50 feet deep and 80 to 100 wide, banks not exceeding some 18 to 20 feet, with a running road for defenders. He describes a bevelled throat at a and a pointed mid-ditch wall at b behind which a road lets defenders shoot at any enemy fallen in and unable to climb out. Sketches of ditch sections and casemates are drawn down the left margin, with figure-words and the letters a, a and b.
On this page
The seven particular parts of a fortress
Having finished the common parts, Leonardo descends to the seven particular ones: the nature of ditches, the forming of ravelins, the outer turrets of the walls, the defences made within the ditches so artillery cannot reach them, the quality of the walls, the drawbridges and corridors, and the principal towers of the castellans.
Proper depth and width of the ditch and its bank
Ditches are better the wider and deeper, their proper measure being 40 to 50 feet deep and 80 to 100 feet wide. The bank's greatest height must not rise above the ditch lest falling earth fill it, and should not exceed 18 to 20 feet. A road 4 to 5 braccia wide runs within the bank, lower than its summit by up to three and a half braccia, so men may circle the ditch unseen.
The bevelled throat at a and the pointed mid-ditch wall at b
At the bank's summit a bevel of 6 to 8 feet with a channel beneath prevents anyone descending without falling headlong, as shown at a. In the middle of the ditch a wall 5 feet thick and 25 feet high is made pointed at the top with a throat on each side, as shown at b, so an enemy fallen in can neither climb it nor return.
Marginal sketches of ditch sections and casemates
Down the left margin are drawn sections through the ditch and its banks, together with hut-like casemate forms, illustrating the profiles the text describes. The figures carry the words for the ditches and casemates and the reference letters used in the prose.